Study of the Effects of a Domain Wall on an Electron Transfer in a Quantum Magnetic Wire

在纳米尺度的金属中，畴壁成核及其动力学已成为当前研究的热点。具体地说，许多研究人员已经报道了铁磁导线中由于DW引起的负磁阻效应对电阻率的影响。此外，在这些含有铁磁畴壁的金属丝中还发现了奇异的非线性输运。为了阐明具有DW的铁磁线的基本特征，我们计算了自旋涨落的激发谱。在研究中，我们考虑了实际样品结构来处理海森堡模型。然后，我们提出了在随机相位近似（RPA）框架下获取结构格林函数的方法。结果表明，低能量激发是由DW引起的，自旋波的特征谱取决于DW的存在和引线的尺寸。在RPA的框架下，研究了DW及其钉住中心对电子传导的影响。我们发现DW由于其周围的自旋涨落而增强了阻力。此外，钉钉中心对抑制自旋波动起着重要的作用，使得DW位于钉钉中心时阻力减小。结果表明，所得结果与实验结果一致。

In the nanometer-scale metals, a domain wall(DW) nucleation and dynamics have become the subjects of current interest. Specifically, the negative magnetoresistance effect on the electrical resistivity due to the DW in ferromagnetic wires has been reported by many researchers. Also, exotic nonlinear transports were reported in these metallic wires containing ferromagnetic domain walls.To elucidate basic features of a ferromagnetic wire with a DW, we calculated the excitation spectrum for the spin fluctuation. In the study, we treated the Heisenberg model with taking the real sample structures into consideration. Then, we presented the method to obtain the Green function for the structure in a framework of the random phase approximation(RPA). It was shown that the low energy excitation is attributed to the DW and the characteristic spin-wave spectrum depends on the existence of the DW and the dimension of leads for the structure.Next, the effects of the DW and its pinning center on the electron conduction are studied in a framework of the RPA. We show that the DW enhances the resistance due to the spin fluctuation around it. Furthermore, the pinning center plays an important role of suppression of the spin fluctuation, which leads to the reduction of the resistance when the DW locates at the pinning center. It is shown that the results obtained are consistent with the experimental findings.